Conventionally, various twin roll continuous casters have been proposed as means for continuously casting metal strip from molten metal.
FIG. 1 shows a strip caster (twin roll continuous caster) disclosed in JP-63-26240A and JP-63-30158A in which reference numerals 1a and 1b denote a pair of inner-cooled casting rolls horizontally arranged side by side in parallel with each other so as to have a nip. Arranged just above the casting rolls 1a and 1b are a tundish 3 and side weirs 3a to provide a molten metal pool 2 between the rolls 1a and 1b. With the molten metal pool 2 being provided between the rolls 1a and 1b, the rolls 1a and 1b on the left and right sides in FIG. 1 are concurrently rotated clockwise and counterclockwise, respectively, so that the metal solidifies between the rolls 1a and 1b into a hot strip 4 with thickness corresponding to the nip between the rolls 1a and 1b and continuously delivered downward of the rolls 1a and 1b. 
Reference numerals 5a and 5b denote a pair of guide pinch roll trains which are arranged just below the rolls 1a and 1b to pinch thickness-wise the hot strip 4 delivered downward from the rolls 1a and 1b. Reference numeral 6 designates a strip guide member in the form of a curved plate when seen sidewise. The guide member 6 is arranged below the pinch roll trains 5a and 5b to horizontally guide the strip delivered downward from the pinch roll trains 5a and 5b. 
Reference numeral 7 denotes a pinch roll unit with pinch rolls 7a and 7b which are arranged downstream of the guide member 6 in the direction of travel of the strip to pinch thickness-wise and convey the strip 4 guided horizontally by the guide member 6.
Reference numeral 8 designates a coiler arranged downstream of the pinch roll unit 7 to wind the strip 4 horizontally fed from the pinch rolls 7a and 7b. 
The above-mentioned travel path of the strip 4, which is constituted by lower halves of the rolls 1a and 1b, the pinch roll trains 5a and 5b, the guide member 6, the pinch roll unit 7 and the coiler 8, is provided within a large-sized gas chamber 9 which accommodates nozzles 10a and 10b arranged between the guide member 6 and the pinch roll unit 7 to confront upper and lower surfaces of the strip 4. The nozzles 10a and 10b are connected via supply pipes 11a and 11b to a gas supply 12; and the gas chamber 9 is connected via feed pipes 13a and 13b to a gas supply 14.
More specifically, in the twin roll continuous caster of FIG. 1, non-oxidative gas such as nitrogen gas is fed from the gas supply 14 via the supply pipes 13a and 13b to the gas chamber 9 to make an interior of the gas chamber 9 into non-oxidative gas atmosphere. The nitrogen gas is injected through the nozzles 10a and 10b via the supply pipes 11a and 11b to suppress formation of scales (oxide layer) on the surface of the strip 4. The temperature of the strip 4 is about 1400° C. when delivered from the rolls 1a and 1b and lowers to about 1000° C. when coming close to the pinch roll unit 7.
As mentioned above, in a metal strip continuous caster, scales must be prevented from being generated on a hot strip produced. To this end, in addition to the system shown in FIG. 1 where the travel path of the strip 4 is wholly enclosed by the large-sized gas chamber 9 to maintain non-oxidative gas atmosphere, various systems have been envisaged. For example, with the travel path of the strip 4 being divided into two at the pinch rolls 7a and 7b, the strip 4 may be enclosed by upstream and downstream gas chambers as well as a roll chamber for the pinch rolls 7a and 7b. In the case of a metal strip continuous caster having.a rolling mill at a subsequent stage (downstream) of the pinch roll unit 7 being utilized, the gas chamber may extend just before the rolling mill. Alternatively, gas chambers may be provided over and before and after the rolling mill. In the above, it is difficult to maintain sealing of the gas chamber and the increase in size of the gas chamber increases the consumption of the non-oxidative gas. Therefore, it is preferable to use smaller-sized gas chamber with smaller capacity.
In any case, the strip is generally enclosed by the gas chamber 9 at least up to the pinch rolls 7a and 7b so that the atmosphere is extremely hot around the pinch rolls 7a and 7b which convey the strip 4 at a temperature of around 1000° C. Such pinch rolls 7a and 7b cannot be cooled by cooling water from outside since water-cooling of the pinch rolls 7a and 7b would cause the gas chamber to be filled with water vapor which would extend to the casting rolls 1a and 1b and adversely affect the hot strip. To overcome this, the pinch rolls 7a and 7b have flow paths therein for communication of cooling water so as to attain internal cooling.
On the other hand, the pinch rolls 7a and 7b used in the twin roll continuous caster have a problem in that the roll surfaces of them tend to roughen in a short period since the pinch rolls 7a and 7b convey the hot strip of around 1000° C.; and there is a further problem that burning or sticking may occur between the pinch rolls 7a and 7b and the strip 4. These may lead to a problem that, upon pinching by the pinch rolls 7a and 7b, roll marks may be formed on the strip 4, resulting in extreme deterioration of surface quality of the strip 4 or failure of obtaining substantial objective products.
Upon occurrence of such problems, the twin roll continuous caster must be stopped in operation to replace the pinch rolls with grinding-finished new pinch rolls for replacement, disadvantageously leading to an increase in the number of line stops needed and lowering of the strip productivity.
Therefore, development of a device has been desired which can be arranged in a narrow space of a gas chamber surrounding a pinch roll unit, permits easy maintenance and can ensure lubrication of a pinch roll to prevent burning or sticking of the pinch roll and prevent roll marks from occurring upon pinching.